Reciprocating air motor exhaust assembly

ABSTRACT

A RECIPROCATING PISTION AIR MOTOR WITH A PILOT PISTON OPERATED SLIDE VALVE THAT ADMITS AIR ALTERNATELY TO OPPOSITE ENDS OF THE DRIVE CYLINDER OF THE AIR MOTOR THROUGH SEPARATE STRAIGHT AIR PASSAGES WHICH ALSO SERVE AS EXHAUST PASSAGES. THE POSITION OF THE DRIVE PISTION IS SENSED BY STEMS EXTENDING FROM SPOOL VALVES POSITIONED AT OPPOSITE ENDS OF THE DRIVE PISTON CYLINDER CHAMBER. THE SPOOL VALVES CONTROL THE SUPPLY AND EXHAUST TO THE PILOT PISTON, THEREBY CONTROLLING THE SLIDE VALVE AND CONSEQUENTLY PRESSURE TO THE DRIVE PISTON.

Nov. 9, T971 R. K. GARDNER ErAL 3,618,458

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United States Patent O 3,618,468 RECIPROCATING AIR MOTOR EXHAUSTASSEMBLY Richard K. Gardner, Montpelier, and Wilbert G. Kautz,

West Unity, Ohio, assignors to The Aro Corporation,

Bryan, Ohio Filed June 24, 1969, Ser. No. 836,037

Int. Cl. F011 25/06 U.S. Cl. 91-306 2 Claims ABSTRACT OF THE DISCLOSUREA reciprocating piston air motor with a pilot piston operated slidevalve that admits air alternately to opposite ends of the drive cylinderof the air motor through separate straight air passages which also serveas exhaust passages. The position of the drive piston is sensed by stemsextending from spool valves positioned at opposite ends of the drivepiston cylinder chamber. The spool valves control the supply and exhaustto the pilot piston, thereby controlling the slide valve andconsequently pressure to the drive piston.

BACKGROUND OF THE INVENTION This invention relates to an improved,reciprocating, fluid driven motor, and in particular to a reciprocating,-uid driven motor that includes a pilot operated slide valve forreversing the direction of the main drive piston of the motor.

Reciprocating type fluid driven motors are common. Also quite common isa reciprocating motor in which a slide valve alternates between twopositions to provide for passage of fluid to one end or the other of thedrive piston of the motor. In the past, however, there have been somedrawbacks in such motors. For example, the power of such motors havebeen restricted because of icing. Icing occurs when the exhaust linesfrom the motor become clogged with ice that forms as moisture in the aircondenses and freezes due to the rapid expansion of the compressed airduring exhaust from the motor. Freezing usually occurs in bends orrestrictions in the exhaust lines leading from the air motor and resultsin blocked air passages. This is just one of the problems that may beencountered with a reciprocating type iiuid motor.

SUMMARY OF THE INVENTION In a principal aspect the present invention ofan improved tiuid driven, reciprocating motor provides a cylinder headfor the motor which includes the fluid inlet and exhaust passages andcooperates with a control valve through which the uid is directedagainst one end or the other of the drive piston of the motor. Thecontrol valve is pilot operated by means for sensing the position of thepiston within the cylinder chamber.

It is thus an object of the present invention to provide an improved,reciprocating piston, uid driven motor.

'It is a further object of the present invention to provide areciprocating piston diuid driven motor with increased power byproviding substantially straight and enlarged inlet and exhaust passagesfrom the opposite ends of the drive cylinder chamber of the motor.

Still another object of the present invention is to provide areciprocating, uid driven motor which includes means for sensing theposition of the drive piston of the motor in order to control reversingof the motor and increasing the speed and eliiciency of the motor.

These and other objects, advantages and features of the invention, willbe set forth in greater detail in the description which follows.

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BRIEF DESCRIPTION OF THE DRAWING In the detailed description whichfollows reference will be made to the drawing comprised of the followingiguresz FIG. l is a top plan, partially cut away view of the improvedmotor of the invention;

FIG. 2 is a cross sectional View of the motor shown in FIG. 3 takensubstantially along the line 2-2 in FIG. 3;

FIG. 3 is a schematic cross sectional Iview of the improved motor of theinvention with the drive piston approaching the cylinder head end of themotor;

FIG. 4 is another schematic cross sectional view showing the drivepiston at the opposite end of the cylinder chamber from that shown inFIG. 3.

FIG. 5 illustrates in graph form comparative data for an old motor, A,and a new motor, B.

DESCRIPTION OF THE PREFERRED EMBODIMENT Attention is initially directedto FIGS. l and 2 which show the construction of a preferred embodimentof the invention. Following this, a description of the mode of operationof the invention is given with reference to FIGS. 3 and 4 for assistancein understanding the cycle of operation of the air motor.

The motor includes a base 10` with a main drive cylinder 12 mounted in acircumferential slot 14 defined in the base 10. A sealing material, forexample, a rubber gasket 16 is positioned in the slot 14 between thecylinder 12 and the base 10. Positioned on top of the cylinder 12 is acylinder head l18 which also includes a circumferential slot 20 with agasket 22 for receipt and sealing of the cylinder 12. Threaded tie rodsas at 23 and nuts as at 25 secure the base 10 and head .18.

A main drive piston 24 is positioned within the cylinder 12 andconnected by means of piston washers 26 and 28 and a hub nut 30` to apiston rod 32. Thus, the rod 32 travels in response to the movement ofthe piston 24. The rod 32 passes through a rod aperture 34 in the base10. An annular plug 38 is threadably inserted in the base 10 to hold ablock 40` in position to bias a spring 42 against sealing washers 44.The washers 44 in combination with an O-ring 46 cooperate to provide aseal about the rod 32 during movement of the rod 32.

Also attached and positioned between the base 10 and head 18 is astraight line tube 48 which is sealed by means of O-ring 501 and 52 incounterbored openings 54 and 56 in the head 18 and base 10 respectively.An inlet or exhaust passage 58, depending upon direction of the piston2'4 movement is defined in the base 10. The passage 58 leads from theinterior of the cylinder 12 through the cylinder port 59 to the tube `48and is substantially of a uniform diameter. The diameter of passage 58is substantially equal to the internal diameter of the tube 48. Passage58 is defined by a center line axis 6.1 which has a substantiallyconstant radius at least equal to the diameter of the passage 58. Thepassage 58 flares outwardly in a frustoconical shape at the cylinderport 59.

The opposite end of the tube 48 connects with a straight line passage 60through the head 18 and a valve plate 62. The valve plate 62 is attachedto the head 18 by means of screws as at 64 with O-ring seals as at 66 toinsure an air-tight seal between the plate 62 and the head 18.

The head 18 and valve plate 62 also include an inlet passage 68 leadingto a cylinder port 69 at the end of the cylinder 12 opposite the passage58. The passages 58 and 68 alternatively act as inlet and exhaustpassages to the cylinder 12. An external liuid or air supply passage 70is also provided for the head 18 leading through the plate 62.

Positioned for slidable movement on the plate 62 is an insert 72. Avalve cover 74 is positioned over the insert 72 and a seal is effectedtherebetween by means of the O- ring 76. This assembly forms the slidevalve generally shown at 75. A collar 78 connected to a pilot piston rod80 is positioned for engagement with the cover 74 to provide coincidentmovement of the valve cover 74 and insert 72 in response to movement ofthe rod 80. In the position shown in FIG. 2, the insert 72 does notprovide connection of the supply passage 70 with either one of the inletpassages 58 or 68. Movement of the insert 72 to the right would providea pressure or driving supply of fluid through the passage 68 to the topof the piston 24. Moving the insert to the left would provide a uidsupply through passage 58. Exhaust is effected through that passage 68or passage 58 not connected with the supply passage 70. This arrangementis distinguished from the common iluid motor arrangement wherein theexhaust passages are alternately connected by means of a slide valve toa single exhaust port with the uid inlet then connecting to the passagenot exhausting.

The exhaust passage 58 and 68 in each case is substantially a straightline exhaust. Moreover, the diameter of the exhaust passages 58 and 68is substantially constant and large in respect to prior artconstructions. The cross sectional area of the passages is preferablyabout 1%i0.2% of the cross sectional area of the cylinder chamber. Thiscompares with an average of 0.5% area ratio in older motors.

Although increasing passage size has been known to improve anti-icingcharacteristics, the combination of large and straight line passages asat 68 and 58 create greater operating efficiency for the reciprocatingmotor and reduce the possibility of icing Also by ducting the exhaustpassages 58 and 68 directly into the atmosphere, greater efciency isrealized. The motor may thus run at greater speeds with greater eciencythan prior motors of this type as can be seen by referring to FIG. 5.

FIG. 5 illustrates comparative data for an old or prior art motor, A,and a new motor, B, which utilizes the present invention. The dashedlines have as their ordinate the air consumption in cubic feet perminute per horsepower. This is the right hand ordinate in FIG. 5. Thesolid lines have as their ordinate horsepower. This is the left handordinate. The abcissa for the g. is cycles per minute. In each case themotor was `utilized to pump iluid having substantially the sameviscosity which for FIG. 5 was less than 1 poise. Also in each case theline pressure to the motors was 120 p.s.i. The data is plotted for amotor having a 31A-inch bore. With the new motor, B, the peak horsepoweris almost three times greater and is provided over a much greater rangethan with the prior art motor, A. Also, the air consumption of the newmotor is almost one-half of the prior art motor. Thus, the new motor isalmost two times as eilicient.

The control means for effecting movement of the slide valve 75 includesthe pilot piston assembly 82 and spool valve assemblies 84 and 86. Asshown in FIG. 1 the pilot piston assembly 82 includes a pilot cylinder88 having therein a pilot piston 90 attached to the rod 80 forreciprocating movement. A bumper 92 is provided at one end of thecylinder 88. The cylinder 88 is held in a housing 94 by means of a cap96. The pilot piston 90 includes seals 98 between the piston 90 andcylinder 88.

Each spool valve assembly 84 and 86 is constructed in a similar manner.Thus, assembly 84 includes a valve chamber 98 with a cover 100 andgasket 102 over the chamber. A valve insert 104 is positioned in thechamber 98 and is biased against a valve washer 106 and seal 108 bymeans of a spacer spring 110. A spool element 112 includes O-rings 114and 116 at its opposite ends. Extending from the end of the spool valveelement 112 nearest drive piston 24 through an opening in the head 18 isa rod or stem 118. The rod or stem 118 is positioned to engage thepiston 24. The other spool assembly 86 is constructed in a similarfashion and also includes a rod or stem 120 for engaging the piston 24.

As illustrated in FIGS. 3 and 4, fluid or pneumatic passageways areprovided to the various sides of the spool valve assemblies 84 and 86and the pilot piston 90. Thus, air, for example, supplied through theinlet or supply passage passes not only through supply passages 58 and68 depending upon the position of the slide valve 75, but also passesthrough a channel 122 in the head 18 to pressurize the upper side of thetop spool valve assembly 84. Inlet pressure is also supplied from thispoint through a channel 124 to the lower end of spool valve assembly 86.The spool valve assembly 84 interconnects one side of pilot piston 90through a channel 123 with either supply inlet 70 or an exhaust outlet126. Spool valve assembly 86 connects the opposite side of pilot piston90 through channel 127 with either supply inlet 70 through channel 122and 124 or an exhaust outlet 128.

In operation, air entering at the air supply or inlet 70 travels throughthe slide valve and the tube 48 aS shown in FIG. 3 forcing the piston 24to the up position. Air above piston 24 exahusts through the port 68.When the piston 24 reaches its extreme up position it engages rod 118forcing the spool valve 112 into an up position, closing passage fromchannel 123 to exhaust 126 and allows air to enter from channel 122through channel 123 to force the pilot piston to the right.Simultaneously, the side valve 75 moves to the right as illustrated inFIG. 4. The opposing air to the right of the pilot piston 90 escapesthrough the channel 127 and out through the exhaust 128.

After the slide valve 75 has moved, air travels down through inlet port68. Air below the piston 24 exhausts through the passage 58, tube 48 andpassage 60. Air pressure on top of spool valve 112 returns spool valve112 and rod 118 to original position connecting channel 123 to exhaust126. When the piston 24 reaches its extreme lower position, it engagesthe rod causing the spool valve assembly 86 to direct air throughchannel 127 from channel 124 to the opposite side of pilot piston 90.Air exhausts from the left side of the pilot piston 90 through channel123 and out exhaust 126.

The stems or rods 118 and .i120 which sense the end of the stroke tooperate the slide valve 75 may be variable in length. It has been foundadvisable to reverse the stroke before the piston 24 bottoms out. Thepiston 24 then cushions on air rather than bottoming out. Therefore, theaction of the motor is smooth and reversal is extremely quick reducingthe pressure flow pulse that would normally be present on reversal of apilot operated motor of this type.

In some instances, however, a measured displacement is desired on thepump end so that the pre-sensing features are eliminated by allowing thepiston 24 to strike the sensing valve and bottom out almostsimultaneously. For example, with a 3% inch bore motor of the typediscussed in relation to FIG. 5, a 1/z-inch stem i118 and 120 providessu'lcient override to prevent bottoming out; whereas, a 1/s-inch stemallows simultaneous reversal and bottoming out and also provides ameasured stroke.

What is claimed is:

1. An improved reciprocating fluid driven motor comprising incombination:

a drive cylinder with a cylinder chamber,

a drive piston positioned to reciprocate in said chamber a cylinder headat each end of said cylinder,

a rst straight-line passage from said cylinder chamber through one ofsaid heads to the atmosphere and a second straight-line passage fromsaid cylinder chamber through said other head, including a single bendand terminating as a straight conduit through said one head to theatmosphere substantially parallel to and adjacent said rst straight-linepassage.

a uid inlet control valve mounted on said one head, said iluid inletcontrol valve including a member which alternately connects a fluidinlet with only one of said passages, the other of said passagesremaining open as a straight-line passage to the atmosphere, one of eachof said passages thereby alternately providing uid for driving saiddrive piston in said cylinder chamber while the other of said passagesexhausts fluid from said cylinder chamber through a straight-linepassage having at the most one single bend in said passage, and

means for driving said uid inlet control valve to a1- ternately connectsaid iluid inlet to one or the other of said passages.

2. The improved .motor of claim 1 wherein said member of said controlvalve comprises an insert with a uid channel adapted to interconnectsaid inlet with only one of said passages and also includes a cover oversaid insert. said including an opening from said channel to said coversuch that fiuid pressure biases said cover away from said insert therebybiasing said insert into substantially fluid tight communication withsaid passages and said inlet.

References Cited UNITEDk STATES PATENTS PAUL E. MASLOUSKY, PrimaryExaminer U.S. Cl. X.R. 91-313

